August 2000
LMC660
CMOS Quad Operational Amplifier
n Ultra low input bias current: 2 fA
General Description
n Input common-mode range includes V-
The LMC660 CMOS Quad operational amplifier is ideal for
n Operating range from +5V to +15V supply
operation from a single supply. It operates from +5V to +15V
n ISS = 375 µA/amplifier; independent of V+
and features rail-to-rail output swing in addition to an input
n Low distortion: 0.01% at 10 kHz
common-mode range that includes ground. Performance
n Slew rate: 1.1 V/µs
limitations that have plagued CMOS amplifiers in the past
are not a problem with this design. Input VOS, drift, and n Available in extended temperature range (-40ÚC to
broadband noise as well as voltage gain into realistic loads +125ÚC); ideal for automotive applications
(2 k&! and 600&!) are all equal to or better than widely ac- n Available to Standard Military Drawing specification
cepted bipolar equivalents.
This chip is built with National s advanced Double-Poly
Applications
Silicon-Gate CMOS process.
n High-impedance buffer or preamplifier
See the LMC662 datasheet for a dual CMOS operational
n Precision current-to-voltage converter
amplifier with these same features.
n Long-term integrator
n Sample-and-Hold circuit
Features
n Peak detector
n Rail-to-rail output swing
n Medical instrumentation
n Specified for 2 k&! and 600&! loads
n Industrial controls
n High voltage gain: 126 dB
n Automotive sensors
n Low input offset voltage: 3 mV
n Low offset voltage drift: 1.3 µV/ÚC
Connection Diagram
14-Pin DIP/SO LMC660 Circuit Topology (Each Amplifier)
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DS008767-1
© 2000 National Semiconductor Corporation DS008767 www.national.com
LMC660 CMOS Quad Operational Amplifier
Absolute Maximum Ratings (Note 3) Power Dissipation (Note 2)
Junction Temperature 150ÚC
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/ ESD tolerance (Note 8) 1000V
Distributors for availability and specifications.
Operating Ratings
Differential Input Voltage Ä…
Supply Voltage
Supply Voltage 16V
Temperature Range
Output Short Circuit to V+ (Note 12)
LMC660AI -40ÚC d" TJ d" +85ÚC
Output Short Circuit to V- (Note 1)
LMC660C 0ÚC d" TJ d" +70ÚC
Lead Temperature
Supply Voltage Range 4.75V to 15.5V
(Soldering, 10 sec.) 260ÚC
Power Dissipation (Note 10)
Storage Temp. Range -65ÚC to +150ÚC
Thermal Resistance (¸JA) (Note 11)
Voltage at Input/Output Pins (V+) + 0.3V, (V-) - 0.3V
14-Pin Molded DIP 85ÚC/W
Current at Output Pin Ä…
18 mA
14-Pin SO 115ÚC/W
Current at Input Pin Ä…
5 mA
Current at Power Supply Pin 35 mA
DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25ÚC. Boldface limits apply at the temperature extremes. V+ =
>
5V, V- = 0V, VCM = 1.5V, VO = 2.5V and RL 1M unless otherwise specified.
Parameter Conditions Typ LMC660AI LMC660C Units
(Note 4)
Limit Limit
(Note 4) (Note 4)
Input Offset Voltage 1 3 6 mV
3.3 6.3 max
Input Offset Voltage 1.3 µV/ÚC
Average Drift
Input Bias Current 0.002 pA
42 max
Input Offset Current 0.001 pA
21 max
>
Input Resistance 1 Tera&!
Common Mode 0V d" VCM d" 12.0V 83 70 63 dB
Rejection Ratio V+ = 15V 68 62 min
Positive Power Supply 5V d" V+ d" 15V 83 70 63 dB
Rejection Ratio VO = 2.5V 68 62 min
Negative Power Supply 0V d" V- d" -10V 94 84 74 dB
Rejection Ratio 83 73 min
Input Common-Mode V+ = 5V & 15V -0.4 -0.1 -0.1 V
Voltage Range For CMRR e" 50 dB 00 max
V+ - 1.9 V+ - 2.3 V+ - 2.3 V
V+ - 2.5 V+ - 2.4 min
Large Signal RL = 2 k&!(Note 5) 2000 440 300 V/mV
Voltage Gain Sourcing 400 200 min
Sinking 500 180 90 V/mV
120 80 min
RL = 600&! (Note 5) 1000 220 150 V/mV
Sourcing 200 100 min
Sinking 250 100 50 V/mV
60 40 min
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LMC660
DC Electrical Characteristics (Continued)
Unless otherwise specified, all limits guaranteed for TJ = 25ÚC. Boldface limits apply at the temperature extremes. V+ =
>
5V, V- = 0V, VCM = 1.5V, VO = 2.5V and RL 1M unless otherwise specified.
Parameter Conditions Typ LMC660AI LMC660C Units
(Note 4)
Limit Limit
(Note 4) (Note 4)
Output Swing V+ = 5V 4.87 4.82 4.78 V
RL = 2 k&!to V+/2 4.79 4.76 min
0.10 0.15 0.19 V
0.17 0.21 max
V+ = 5V 4.61 4.41 4.27 V
RL = 600&! to V+/2 4.31 4.21 min
0.30 0.50 0.63 V
0.56 0.69 max
V+ = 15V 14.63 14.50 14.37 V
RL = 2 k&!to V+/2 14.44 14.32 min
0.26 0.35 0.44 V
0.40 0.48 max
V+ = 15V 13.90 13.35 12.92 V
RL = 600&! to V+/2 13.15 12.76 min
0.79 1.16 1.45 V
1.32 1.58 max
Output Current Sourcing, VO = 0V 221613 mA
V+ = 5V 14 11 min
Sinking, VO = 5V211613 mA
14 11 min
Output Current Sourcing, VO = 0V 402823 mA
V+ = 15V 25 21 min
Sinking, VO = 13V 39 28 23 mA
(Note 12) 24 20 min
Supply Current All Four Amplifiers 1.5 2.2 2.7 mA
VO = 1.5V 2.6 2.9 max
AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25ÚC. Boldface limits apply at the temperature extremes. V+ =
>
5V, V- = 0V, VCM = 1.5V, VO = 2.5V and RL 1M unless otherwise specified.
Parameter Conditions Typ LMC660AI LMC660C Units
(Note 4)
Limit Limit
(Note 4) (Note 4)
Slew Rate (Note 6) 1.1 0.8 0.8 V/µs
0.6 0.7 min
Gain-Bandwidth Product 1.4 MHz
Phase Margin 50 Deg
Gain Margin 17 dB
Amp-to-Amp Isolation (Note 7) 130 dB
Input Referred Voltage Noise F = 1 kHz 22
Input Referred Current Noise F = 1 kHz 0.0002
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LMC660
AC Electrical Characteristics (Continued)
Unless otherwise specified, all limits guaranteed for TJ = 25ÚC. Boldface limits apply at the temperature extremes. V+ =
>
5V, V- = 0V, VCM = 1.5V, VO = 2.5V and RL 1M unless otherwise specified.
Parameter Conditions Typ LMC660AI LMC660C Units
(Note 4)
Limit Limit
(Note 4) (Note 4)
Total Harmonic Distortion F = 10 kHz, 0.01 %
AV = -10
RL = 2 k&!,
VO = 8 VPP
V+ = 15V
Note 1: Applies to both single supply and split supply operation. Continuous short circuit operation at elevated ambient temperature and/or multiple Op Amp shorts
Ä…
can result in exceeding the maximum allowed junction temperature of 150ÚC. Output currents in excess of 30 mA over long term may adversely affect reliability.
Note 2: The maximum power dissipation is a function of TJ(max), ¸JA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max)
- TA)/¸JA.
Note 3: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is in-
tended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The
guaranteed specifications apply only for the test conditions listed.
Note 4: Typical values represent the most likely parametric norm. Limits are guaranteed by testing or correlation.
Note 5: V+ = 15V, VCM = 7.5V and RL connected to 7.5V. For Sourcing tests, 7.5V d" VO d" 11.5V. For Sinking tests, 2.5V d" VO d" 7.5V.
Note 6: V+ = 15V. Connected as Voltage Follower with 10V step input. Number specified is the slower of the positive and negative slew rates.
Note 7: Input referred. V+ = 15V and RL = 10 k&! connected to V+/2. Each amp excited in turn with 1 kHz to produce VO = 13 VPP.
Note 8: Human body model, 1.5 k&! in series with 100 pF.
Note 9: A military RETS electrical test specification is available on request. At the time of printing, the LMC660AMJ/883 RETS spec complied fully with the boldface
limits in this column. The LMC660AMJ/883 may also be procured to a Standard Military Drawing specification.
Note 10: For operating at elevated temperatures the device must be derated based on the thermal resistance ¸JA with PD = (TJ - TA)/¸JA.
Note 11: All numbers apply for packages soldered directly into a PC board.
Note 12: Do not connect output to V+ when V+ is greater than 13V or reliability may be adversely affected.
Ä…
Typical Performance Characteristics VS = 7.5V, TA = 25ÚC unless otherwise specified
Supply Current
Offset Voltage
Input Bias Current
vs Supply Voltage
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Output Characteristics
Output Characteristics
Input Voltage Noise
Current Sinking
Current Sourcing
vs Frequency
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DS008767-29
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LMC660
Ä…
Typical Performance Characteristics VS = 7.5V, TA = 25ÚC unless otherwise specified (Continued)
CMRR vs Frequency
Open-Loop Frequency
Frequency Response
Response
vs Capacitive Load
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DS008767-32
Non-Inverting Large Signal
Stability vs
Stability vs
Pulse Response
Capacitive Load
Capacitive Load
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DS008767-34
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Note: Avoid resistive loads of less than 500&!, as they may cause instability.
Application Hints
Amplifier Topology
The topology chosen for the LMC660, shown in Figure 1, is
unconventional (compared to general-purpose op amps) in
that the traditional unity-gain buffer output stage is not used;
instead, the output is taken directly from the output of the in-
tegrator, to allow rail-to-rail output swing. Since the buffer
traditionally delivers the power to the load, while maintaining
high op amp gain and stability, and must withstand shorts to
either rail, these tasks now fall to the integrator.
As a result of these demands, the integrator is a compound
affair with an embedded gain stage that is doubly fed forward
DS008767-4
(via Cf and Cff) by a dedicated unity-gain compensation
driver. In addition, the output portion of the integrator is a
FIGURE 1. LMC660 Circuit Topology (Each Amplifier)
push-pull configuration for delivering heavy loads. While
sinking current the whole amplifier path consists of three The large signal voltage gain while sourcing is comparable
gain stages with one stage fed forward, whereas while to traditional bipolar op amps, even with a 600&! load. The
sourcing the path contains four gain stages with two fed gain while sinking is higher than most CMOS op amps, due
forward. to the additional gain stage; however, under heavy load
(600&!) the gain will be reduced as indicated in the Electrical
Characteristics.
Compensating Input Capacitance
The high input resistance of the LMC660 op amps allows the
use of large feedback and source resistor values without los-
ing gain accuracy due to loading. However, the circuit will be
especially sensitive to its layout when these large-value re-
sistors are used.
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LMC660
Application Hints (Continued)
Every amplifier has some capacitance between each input
and AC ground, and also some differential capacitance be-
the feedback capacitor should be:
tween the inputs. When the feedback network around an
amplifier is resistive, this input capacitance (along with any
additional capacitance due to circuit board traces, the
socket, etc.) and the feedback resistors create a pole in the
feedback path. In the following General Operational Amplifier
Note that these capacitor values are usually significant
circuit, Figure 2 the frequency of this pole is
smaller than those given by the older, more conservative for-
mula:
where CS is the total capacitance at the inverting input, in-
cluding amplifier input capcitance and any stray capacitance
from the IC socket (if one is used), circuit board traces, etc.,
and RP is the parallel combination of RF and RIN. This for-
mula, as well as all formulae derived below, apply to invert-
ing and non-inverting op-amp configurations.
When the feedback resistors are smaller than a few k&!, the
frequency of the feedback pole will be quite high, since CS is
generally less than 10 pF. If the frequency of the feedback
pole is much higher than the  ideal closed-loop bandwidth
(the nominal closed-loop bandwidth in the absence of CS),
the pole will have a negligible effect on stability, as it will add
only a small amount of phase shift.
DS008767-6
However, if the feedback pole is less than approximately 6 to
CS consists of the amplifier s input capacitance plus any stray capacitance
from the circuit board and socket. CF compensates for the pole caused by
10 times the  ideal -3 dB frequency, a feedback capacitor,
CS and the feedback resistors.
CF, should be connected between the output and the invert-
FIGURE 2. General Operational Amplifier Circuit
ing input of the op amp. This condition can also be stated in
terms of the amplifier s low-frequency noise gain: To main-
Using the smaller capacitors will give much higher band-
tain stability a feedback capacitor will probably be needed if
width with little degradation of transient response. It may be
necessary in any of the above cases to use a somewhat
larger feedback capacitor to allow for unexpected stray ca-
pacitance, or to tolerate additional phase shifts in the loop, or
excessive capacitive load, or to decrease the noise or band-
where
width, or simply because the particular circuit implementa-
tion needs more feedback capacitance to be sufficiently
stable. For example, a printed circuit board s stray capaci-
tance may be larger or smaller than the breadboard s, so the
is the amplifier s low-frequency noise gain and GBW is the actual optimum value for CF may be different from the one
amplifier s gain bandwidth product. An amplifier s low- estimated using the breadboard. In most cases, the values
frequency noise gain is represented by the formula of CF should be checked on the actual circuit, starting with
the computed value.
Capacitive Load Tolerance
Like many other op amps, the LMC660 may oscillate when
its applied load appears capacitive. The threshold of oscilla-
regardless of whether the amplifier is being used in inverting
tion varies both with load and circuit gain. The configuration
or non-inverting mode. Note that a feedback capacitor is
most sensitive to oscillation is a unity-gain follower. See
more likely to be needed when the noise gain is low and/or
Typical Performance Characteristics.
the feedback resistor is large.
The load capacitance interacts with the op amp s output re-
If the above condition is met (indicating a feedback capacitor
sistance to create an additional pole. If this pole frequency is
will probably be needed), and the noise gain is large enough
sufficiently low, it will degrade the op amp s phase margin so
that:
that the amplifier is no longer stable at low gains. As shown
in Figure 3, the addition of a small resistor (50&! to 100&!) in
series with the op amp s output, and a capacitor (5 pF to
10 pF) from inverting input to output pins, returns the phase
margin to a safe value without interfering with lower-
the following value of feedback capacitor is recommended:
frequency circuit operation. Thus larger values of capaci-
tance can be tolerated without oscillation. Note that in all
cases, the output will ring heavily when the load capacitance
is near the threshold for oscillation.
If
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LMC660
rings for standard op-amp configurations. If both inputs are
Application Hints (Continued)
active and at high impedance, the guard can be tied to
ground and still provide some protection; see Figure 6d.
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FIGURE 3. Rx, Cx Improve Capacitive Load Tolerance
Capacitive load driving capability is enhanced by using a pull
up resistor to V+ (Figure 4). Typically a pull up resistor con-
ducting 500 µA or more will significantly improve capacitive
load responses. The value of the pull up resistor must be de-
termined based on the current sinking capability of the ampli-
fier with respect to the desired output swing. Open loop gain
of the amplifier can also be affected by the pull up resistor
DS008767-16
(see Electrical Characteristics).
FIGURE 5. Example, using the LMC660,
of Guard Ring in P.C. Board Layout
DS008767-23
FIGURE 4. Compensating for Large Capacitive Loads
with a Pull Up Resistor
PRINTED-CIRCUIT-BOARD LAYOUT
FOR HIGH-IMPEDANCE WORK
It is generally recognized that any circuit which must operate
with less than 1000 pA of leakage current requires special
layout of the PC board. When one wishes to take advantage
of the ultra-low bias current of the LMC662, typically less
than 0.04 pA, it is essential to have an excellent layout. For-
tunately, the techniques for obtaining low leakages are quite
simple. First, the user must not ignore the surface leakage of
the PC board, even though it may sometimes appear accept-
ably low, because under conditions of high humidity or dust
or contamination, the surface leakage will be appreciable.
To minimize the effect of any surface leakage, lay out a ring
of foil completely surrounding the LMC660 s inputs and the
terminals of capacitors, diodes, conductors, resistors, relay
terminals, etc. connected to the op-amp s inputs. See Figure
5. To have a significant effect, guard rings should be placed
on both the top and bottom of the PC board. This PC foil
must then be connected to a voltage which is at the same
voltage as the amplifier inputs, since no leakage current can
flow between two points at the same potential. For example,
a PC board trace-to-pad resistance of 1012&!, which is nor-
mally considered a very large resistance, could leak 5 pA if
the trace were a 5V bus adjacent to the pad of an input. This
would cause a 100 times degradation from the LMC660 s ac-
tual performance. However, if a guard ring is held within
5 mV of the inputs, then even a resistance of 1011&! would
cause only 0.05 pA of leakage current, or perhaps a minor
(2:1) degradation of the amplifier s performance. See Figure
6a, Figure 6b, Figure 6c for typical connections of guard
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LMC660
Application Hints (Continued)
DS008767-21
(Input pins are lifted out of PC board and soldered directly to components.
All other pins connected to PC board.)
DS008767-17
FIGURE 7. Air Wiring
(a) Inverting Amplifier
BIAS CURRENT TESTING
The test method of Figure 8 is appropriate for bench-testing
bias current with reasonable accuracy. To understand its op-
eration, first close switch S2 momentarily. When S2 is
opened, then
DS008767-18
(b) Non-Inverting Amplifier
DS008767-19
(c) Follower
DS008767-22
FIGURE 8. Simple Input Bias Current Test Circuit
A suitable capacitor for C2 would be a 5 pF or 10 pF silver
mica, NPO ceramic, or air-dielectric. When determining the
magnitude of Ib-, the leakage of the capacitor and socket
DS008767-20
must be taken into account. Switch S2 should be left shorted
(d) Howland Current Pump
most of the time, or else the dielectric absorption of the ca-
pacitor C2 could cause errors.
FIGURE 6. Guard Ring Connections
Similarly, if S1 is shorted momentarily (while leaving S2
The designer should be aware that when it is inappropriate
shorted)
to lay out a PC board for the sake of just a few circuits, there
is another technique which is even better than a guard ring
on a PC board: Don t insert the amplifier s input pin into the
board at all, but bend it up in the air and use only air as an in-
sulator. Air is an excellent insulator. In this case you may
where Cx is the stray capacitance at the + input.
have to forego some of the advantages of PC board con-
struction, but the advantages are sometimes well worth the
effort of using point-to-point up-in-the-air wiring. See Figure
7.
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LMC660
Typical Single-Supply Applications (V+ = 5.0 VDC)
Additional single-supply applications ideas can be found in
the LM324 datasheet. The LMC660 is pin-for-pin compatible
Sine-Wave Oscillator
with the LM324 and offers greater bandwidth and input resis-
tance over the LM324. These features will improve the per-
formance of many existing single-supply applications. Note,
however, that the supply voltage range of the LMC660 is
smaller than that of the LM324.
Low-Leakage Sample-and-Hold
DS008767-7
DS008767-9
Instrumentation Amplifier Oscillator frequency is determined by R1, R2, C1, and C2:
fosc = 1/2Ä„RC, where R = R1 = R2 and
C = C1 = C2.
This circuit, as shown, oscillates at 2.0 kHz with a peak-to-
peak output swing of 4.5V.
1 Hz Square-Wave Oscillator
DS008767-8
If R1 = R5, R3 = R6, and R4 = R7; then
DS008767-10
4"
AV H"100 for circuit shown.
Power Amplifier
For good CMRR over temperature, low drift resistors should
be used. Matching of R3 to R6 and R4 to R7 affect CMRR.
Gain may be adjusted through R2. CMRR may be adjusted
through R7.
DS008767-11
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LMC660
Typical Single-Supply Applications
1 Hz Low-Pass Filter
(V+ = 5.0 VDC) (Continued)
(Maximally Flat, Dual Supply Only)
10 Hz Bandpass Filter
DS008767-14
fc = 1 Hz
DS008767-12 d = 1.414
Gain = 1.57
fO = 10 Hz
Q = 2.1
Gain = -8.8
High Gain Amplifier with Offset
10 Hz High-Pass Filter
Voltage Reduction
DS008767-13
fc = 10 Hz
d = 0.895
Gain = 1
2 dB passband ripple
DS008767-15
Gain = -46.8
Output offset voltage reduced to the level of the input offset voltage of the
bottom amplifier (typically 1 mV).
Ordering Information
Package Temperature Range NSC Transport
Drawing Media
Industrial Commercial
-40ÚC to +85ÚC 0ÚC to +70ÚC
14-Pin LMC660AIM LMC660CM M14A Rail
Small Outline LMC660AIMX LMC660CMX Tape and Reel
14-Pin LMC660AIN LMC660CN N14A Rail
Molded DIP
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LMC660
Physical Dimensions inches (millimeters) unless otherwise noted
Small Outline Dual-In-Line Pkg. (M)
Order Number LMC660AIM, LMC660CM or LMC660AIMX
NS Package Number M14A
Molded Dual-In-Line Pkg. (N)
Order Number LMC660AIN, LMC660CN or LMC660CNX
NS Package Number N14A
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LMC660
Notes
LIFE SUPPORT POLICY
NATIONAL S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or 2. A critical component is any component of a life
systems which, (a) are intended for surgical implant support device or system whose failure to perform
into the body, or (b) support or sustain life, and can be reasonably expected to cause the failure of
whose failure to perform when properly used in the life support device or system, or to affect its
accordance with instructions for use provided in the safety or effectiveness.
labeling, can be reasonably expected to result in a
significant injury to the user.
National Semiconductor National Semiconductor National Semiconductor National Semiconductor
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National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
LMC660 CMOS Quad Operational Amplifier